#include <vector>
#include <string>
#include <unordered_map>
#include <algorithm>

using namespace std;

class Solution {
public:
    // 516. 最长回文子序列
    // https://leetcode.cn/problems/longest-palindromic-subsequence/
    int longestPalindromeSubseq(string s) {
        int n = s.size();
        vector<vector<int>> dp(n, vector<int>(n));

        int ans = 0;
        for (int i = n-1; i>=0; --i)
        {
            for (int j = i; j<n; ++j)
            {
                if (s[i] == s[j])
                {
                    if (i==j) dp[i][j] = 1;
                    else if (i+1==j) dp[i][j] = 2;
                    else dp[i][j] = dp[i+1][j-1] + 2;
                }
                else
                    dp[i][j] = max(dp[i][j-1], dp[i+1][j]);
                
                ans = max(ans, dp[i][j]);
            }
        }

        return ans;
    }

    // 1312. 让字符串成为回文串的最少插入次数
    // https://leetcode.cn/problems/minimum-insertion-steps-to-make-a-string-palindrome/
    int minInsertions(string s) {
        int n = s.size();
        vector<vector<int>> dp(n, vector<int>(n));
        
        for (int i = n-1; i>=0; --i)
        {
            for (int j = i; j<n; ++j)
            {
                if (s[i] == s[j])
                    dp[i][j] = i+1<j ? dp[i+1][j-1] : 0;
                else 
                    dp[i][j] = min(dp[i][j-1] + 1, dp[i+1][j] + 1);
            }
        }

        return dp[0][n-1];
    }
};